Currently, antifuse structures are generally based on the breakdown of an oxide located between an active region of an integrated circuit and a polysilicon line. Before the oxide undergoes electrical breakdown, it is an insulator and no current passes between the polysilicon line and the active region of the integrated circuit.
However, when a breakdown potential difference is applied between the polysilicon line and the active zone of the integrated circuit, the oxide then undergoes breakdown and becomes a conductor.
Breakdown is irreversible.
Thus, such an antifuse structure may behave in operation as a one-time programmable memory cell (OTP cell).
Specifically, the memory cell then passes from a non-conductive state to a conductive state, which makes it possible to store a bit the logic value of which depends on the state of the memory cell.
Antifuse structures are often used in products. Additionally, when they are used to code secret information, they are then subject to reverse engineering.
However, the current antifuse structures can easily be observed by failure analysis using suitable tools such as scanning electron microscopes (SEM), which make it possible, after removal of the polysilicon layer, to determine the state of the oxide.